1. Field of the Invention
The present invention relates to a braking device for rail vehicles. More specifically, the invention relates to a compact actuator for a disc-type brake.
2. Description of the Prior Art
The prior art device is illustrated in Federal Republic of Germany Patent No. 20 26 545. This device is further illustrated in FIG. 1. An understanding of the operation of the prior art device is obtained with reference to FIG. 1. FIG. 2, while illustrating the improved device, shows in additional the basic operation of disc-type brakes with regard to the application of the pads to the wheel or disc rotor. As seen in FIG. 2, a disc-brake actuator is utilized for applying pressure, through two disc-brake pads, to the opposite sides of a revolving wheel or rotor. The disc-brake actuator operates by outward lateral movement of an actuator 21 (as shown in FIG. 2) by moment arm 25, which displaces first lever arm 20 outwardly from the valve housing 5. As the distance between pivots 7 and 22 increases, and the distance between pivots 9 and 16 is held constant by connecting rod 15, pads 13 and 11 are forced against wheel 12.
Referring to FIG. 1, an actuator is disclosed which can be both spring applied-air release and air applied-spring release. The release of the brake is produced by a moment arm 125, corresponding to moment arm 25 of the improved device, urged in a leftmost, non-braking direction by spring 100. The corresponding air application of the service brake is provided by pressurization of chamber 104, when air is introduced to chamber 104, piston 106 is moved rightwardly, as shown in FIG. 1, moving moment arm 125 into the actuated position.
The spring applied-air release function is performed by spring 131, piston 115 and chamber 105. Pressure is maintained in chamber 105 while braking is not required. When spring actuated braking is desired, pressure is relived from chamber 105 through port 110. This allows piston 115 to move rightwardly, as shown in FIG. 1 as urged by spring 131. This draws transfer arm 120 and flange 130 rightwardly, which in turn moves moment arm 125 rightwardly, engaging the brake. As is quickly discerned from FIG. 1, a supplemental housing 135 is necessary to contain the mechanism of the actuator.
This braking device therefore requires a relatively large space for the actuation elements, as a result of which the entire braking device is relatively large. What is lacking in the art, therefore, is a braking device of the above type, which has a smaller construction compared with the above-described braking device.